The development of effective means for treating foot sores or ulcerations, especially diabetic foot ulcerations, presents a significant medical challenge. Diabetic foot ulcers result in more than 55,000 lower extremity amputations per year (nearly half of all amputations performed in the United States) and account for more hospitalizations than any other single complication of diabetes. Of the 14 million diagnosed diabetics, 15 percent, or 2.1 million, suffer from foot ulcerations. In fact, foot ulcers are the leading cause of hospitalization of patients with diabetes and account for 10 percent of the costs related to diabetic care.
The burdens of such complications can also have a devastating effect on patients and their families. Patients' quality of life can rapidly decline leaving them unable to work, and dependent on family members to spend their time and resources caring for the patient. Disabilities due to diabetes result in more than $5.6 billion per year in lost wages and earnings.
The problem is compounded by the fact that many diabetics suffer from peripheral neuropathy and thus cannot feel pain. Since pain is often a primary incentive for patient compliance, neuropathy patients frequently do not comply with voluntary off-weighting techniques, resulting in further deterioration of the wound and possibly leading to infection. It is, therefore, crucial that the off-weighting treatment device does not set patients up for failure by allowing them to walk on the wound, thus preventing healing.
The typical cycle for this medical complication is chronic foot ulceration, infection, hospitalization, amputation and rehabilitation. This costly cascade of events need not take place since two-thirds of diabetic amputees do have an adequate blood supply to heal ulcerations. The key factor for effective treatment then is to remove the patient's weight from the ulcerated site to give the ulcers an opportunity to heal.
Currently, there are several options for off-weighting diabetic foot ulcers to enable them to heal. These options have varying degrees of success depending upon the degree of patient compliance, wound location, and grade of wound. The following is a brief description of the most frequently used therapies for treating diabetic foot ulcers and their advantages and disadvantages.
Prescribing the use of crutches and/or wheelchair use is perhaps one of the simpler treatment methods. However, these options have produced poor clinical results due to lack of patient compliance. Patients with peripheral neuropathy in particular are not motivated to use these devices.
A variety of specially designed sandals and modified shoes have been tried. One sandal, referred to as the temporary healing sandal, provides a cut-out region in the sole to alleviate pressure to the ulcerated site. The problem with this type of sandal is that since the human foot is not flat, when pressure is removed from the area of the ulcer site, there is increased pressure to other metatarsal heads which creates the potential for transfer lesions. A second sandal, the custom sandal, is made from an impression of the patient's foot. Like the temporary sandal, an area in the sole aligned with the location of the ulcers is cut out to relieve pressure at the ulcerated site. Because the patient's weight is more evenly distributed as compared to the temporary healing sandal, the likelihood of transfer lesions being formed is reduced. However, this type of sandal provides no relief from shearing forces.
Several devices generically referred to as "walkers" have been designed which are similar to the sandals just described. The DH Walker, for example, is similar in design to the temporary healing sandal. It includes a flat surface upon which the foot rests, but the surface includes plugs which can be removed to accommodate the area of the wound. Not surprisingly given the similarity in design, the DH Walker suffers from the same problem as the temporary sandal in that weight is transferred to adjacent metatarsal heads and the potential for the formation of transfer lesions is great. The sandal also fails to alleviate shearing forces. Another walker called the Cam Walker is essentially equivalent to a DH walker, except that it does not have removable plugs within the device. Consequently, the Cam Walker does not effectively off-weight the wound.
A variety of modified shoes have been tried. Ipos shoes are half shoes that are cut off at the middle of the foot, leaving the forefoot overhanging the cut-off area. Studies have shown that this shoe can be effective, provided the patient is diligent in wearing it. Compliance during the evening, however, is often a problem. Moreover, the Ipos shoe is only applicable to forefoot ulcers and has a high potential for generating transfer lesions.
A different approach involves placing felt directly on the foot and then covering the felt with foam which includes a cut-out region to correspond to the location of the wound. This approach has been shown to be efficacious. However, the method can also cause damage to the skin during the removal process, since the plantar skin can be easily torn.
The Charcot Restraint Orthotic Walker (C.R.O.W.) is a cast manufactured of polypropylene which is effective in the treatment of plantar ulcerations, but only so long as the leg remains the size it was when first casted. Cost is another problem; the average casting cost is $1,200 per cast. In general, C.R.O.W.s have shown limited utility since changes in the patients' leg reduce the effectiveness at which the foot is off-weighted over time.
All of these methods have proven successful provided they are used on the right patient at the right time, and that patient compliance is not an issue. However, the primary current ambulatory method that ensures off-weighting of the wound is the Total Contact Cast (TCC). The TCC is a cast that is formed using a complicated procedure involving wrapping the patient's leg in plaster wrap and fiberglass. Although the TCC has the disadvantage of being difficult to apply, it has been shown to be effective in healing up to 90 percent of cases.
Total contact casts relieve the forces that prevent healing by: 1) shortening stride length, 2) decreasing walking velocity (which diminishes vertical forces), 3) eliminating motion at the ankle joint (sagittal plane), 4) eliminating the propulsive phase of gait, 5) redirecting body weight from the foot to the lower leg, and 6) eliminating shearing forces. One study concluded that the effectiveness of the TCC is a consequence of its ability to decrease plantar pressures to nearly imperceptible levels (as low as 0.34 N/cm.sup.2) and to essentially eliminate motion in the cast, thus substantially curtailing shearing forces (Todd, W. F., et al. Wound/Ostomy Management, 41: 48-49, 1995).
Yet, despite its efficacy when used properly, numerous difficulties have resulted in significantly lower TCC usage than might be expected. First, application of the total contact cast is a complex, 15-step process requiring a high degree of skill and approximately one hour of time to complete. Improper application can also have significant negative consequences. For example, casts applied over an active infection raise the potential for loss of the infected leg, improper application of the cast can create new ulcerations, and the failure to remove wrinkles in the stocking inside the cast may irritate the patient's skin.
Secondly, the TCC cannot accommodate the changes in patient leg size which frequently occur due to decreased edema and atrophy of the muscle. Typically, the patient must be re-examined three days after the initial casting to check for decreases in leg volume that could allow the leg to "piston" (slide) within the cast. Pistoning requires immediate recasting. Casts that consistently piston call for weekly recasting. Even casts that do not piston must still be changed at least every two weeks. Patients with large wounds may require recasting twice per week. Patients must be vigilant for abnormalities which require an immediate cast change. Thus, the complexity of the casting process is compounded by the frequent need for a recasting and the high cost of multiple applications.
Finally, cast removal is also difficult, and improper removal can have adverse consequences. For example, because there is little or no interior padding in the TCC, utilizing a saw to remove the cast without cutting, abrading or burning the patient requires significant practice. Incorrect technique can result in lacerations to the patient's leg.
For the foregoing reasons, many physicians have opted to use other methods for treating plantar ulcers. Moreover, even if physicians could be properly trained on a widespread scale to apply and remove the TCC, it is doubtful that use of the TCC would increase significantly since many practitioners find that such time-consuming and labor intensive procedures are not profitable.
While the TCC and the other devices listed above have been specifically designed to address the need to treat patients suffering plantar ulcers, it should also be noted that a number of related adjustable leg casts have also been developed. These casts have significant advantages since they are adjustable and reuseable. These casts, however, differ from the TCC and the brace of the present invention in that the casts are designed primarily for fracture care rather than for treating plantar ulcers.
One example of such a cast is described in U.S. Pat. Nos. 3,580,248 and 3,701,349 to Larson. The cast includes two rigid, plastic shells, each containing an inflatable air bag disposed therein. These air bags run essentially the full length of the cast and filly surround the leg. Once a patient's leg is inserted into cast and the two halves fastened together, air can be used to inflate the bags to create a pressure against the leg for immobilizing the fractured limb.
A second example of such a cast includes the one described in U.S. Pat. No. 3,995,565 to Johnson, Jr. This cast is quite similar in construction to that described in the Larson patents and is also designed to treat fractures. However, the shells in the Johnson cast have sufficient flexibility so that the edges of one shell can be flexed to fit over the edges of the other shell. This enables the two shells to be radially adjusted with respect to each other to increase and decrease the size of the cast interior, thereby allowing the cast to accommodate a variety of leg sizes. Like the Larson cast, the Johnson cast includes air bags in both shell halves. Unlike the Larson cast, inflated air bags need not fully surround the leg; rather there are sections in which the shell and a portion of the leg are in indirect abutting relationship, the shell and leg only being separated by an uninflated portion of the air bag.
Because these casts are designed primarily for fracture care, they function quite differently than the brace of the current invention. As casts, these devices are designed primarily to immobilize an area surrounding the fracture; in particular, the casts are designed primarily to prevent flexing of the fracture. The device of the current invention, however, is not a cast but a brace. It is designed not to simply prevent a bone from flexing, but acts to redirect or redistribute a patient's weight throughout the brace itself rather than the patients foot More specifically, the brace of the present invention accomplishes the more difficult goals of effectively off-weighting the plantar surface of a patients foot, immobilizing the patient's ankle to prevent plantar flexing and significantly reducing shearing forces at the plantar surface. Existing casts do not appear to effectively achieve all of these results.
Thus, in view of the limitations of the current devices specifically designed for treating plantar ulcers, as well as casts designed for fracture care, there is a need for a device which is equally effective as the TCC in treating patients suffering from plantar ulcerations but without its associated limitations. In particular, there is a need for a brace which off-weights the plantar surface and prevents flexing of the foot within the brace in order to minimize the shearing forces on the ulcerated sites and promote rapid healing. Unlike the TCC, however, the brace should be easily applied and removed, reuseable and adjustable.